During the past two years, we have accumulated a large amount of information on approximately 16,000 physicians and 10,000 lawyers who were respectively licensed to practice medicine in Connecticut or admitted to the Connecticut Bar between 1900 and 1975. This unique collection of data was obtained in order to compare survival and estimate the respective risks of cancer as a cause of death in these two professional groups with different exposures to cancer patients but similar life style and socio-economic status. In the present study we propose to ascertain more accurately the cancer experience of physicians and lawyers who have died by examining death certificates and coding all causes of death and associated conditions as listed on these records. Any cancer mentioned, whether or not listed as the "underlying cause of death" will be included in the analysis. Detailed information on successive specialties practiced by each physician throughout life will enable us to search for associated cancer risks which may occur following professional exposure to cancer in the clinical or laboratory environment.